Nozzle control device with closed loop control circuit for an air weaving loom

ABSTRACT

A nozzle control device for an air weaving loom has a weft thread insertion by one or more main nozzles and a feed advance of the yarn in the air insertion channel by relay nozzles arranged one behind the other at the weaving reed. The relay nozzles are controlled in groups and in sequence in an impulse type manner in such a way that the thread tip zone is seized by the air stream and the thread is pulled through the air insertion channel. The control of the relay nozzles of an air weaving machine is accomplished in such a way that in sequential work steps substantially different types of yarns can be woven with a high quality. For this purpose the durations of air impulses supplied to the relay nozzles arranged in groups, are controlled as a function of yarn specific values modified by a currently measured air effectiveness of the respective yarn being processed.

FIELD OF THE INVENTION

The invention relates to a nozzle control device for an air jet weavingloom with a weft thread insertion by one or more main nozzles and by aplurality of relay nozzles arranged along a weft thread insertion airchannel.

BACKGROUND INFORMATION

The weft thread insertion in conventional air weaving looms takes placethrough one or several main nozzles, whereby each main nozzle iscoordinated with one yarn. The main nozzles are arranged in bundles andso centered on the air insertion channel that each time one yarn can becarried into the air insertion channel.

The yarn is transported through the weft thread insertion air channel inthat an air guiding of the weft thread through the insertion air channeltakes place by means of relay nozzles arranged in a row along theinsertion air channel through the weaving reed.

Heretofore, the relay nozzles have been controlled in sequence in animpulse type manner, so that the thread tip was seized by the air streamfor pulling the thread through the insertion air channel.

It has been a disadvantage in conventional controls of the relay nozzlesin air weaving looms that the impulse duration of the control of therelay nozzles had to be adjusted to the thickest thread which is leastair effective. It was necessary to take care that the heaviest threadwas still sufficiently exposed along its length to the air flow, so thateven the thickest thread achieved the speed sufficient for its transportthrough the insertion air channel. Supplying air in accordance with therequirements of the heaviest thread has the disadvantage that, if lessheavy yarns are simultaneously woven, these lighter more air effectiveyarns receive too much air, whereby the excess air is wasted. On the onehand, the wasted air caused a disadvantageously high air consumptionand, on the other hand, it involved the danger of damaging the yarn. Inbad cases it was no longer possible to weave substantially differentyarns into the same fabric.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the invention to further develop the control deviceof the relay nozzles of an air weaving machine in such a manner that insequential work steps substantially different yarns can be woven with ahigh quality.

For achieving the above object the invention is characterized in thatthe relay nozzles are controlled in groups and in that the air impulseduration of the control device is controlled in a closed loop manner inresponse to the air effectiveness of the respective yarn being woven,whereby said air effectiveness or its relevant parameter is currentlymeasured automatically and the respective signal is used in said closedloop control for controlling said air impulse duration.

The ratio of the supporting surface of the yarn in air, relative to theyarn mass is defined as a parameter of the air effectiveness. Thus, itbecomes clear that light yarns require a different control of the airnozzles than comparatively heavy yarns.

According to a further embodiment of the invention, a known parameter ofthe air effectiveness of a particular yarn type is also taken intoaccount for the control by manual insertion of the known parameter intoa control device by means of an operating terminal.

In another embodiment the current relevant parameters of the yarn areascertained by way of a thickness measurement. Such a measurementprovides information regarding the hairiness of the weft thread which isdirectly relevant to the air effectiveness of that weft thread. Thespecific or current parameters of the yarn can be ascertainedcapacitively by sensors measuring an electrical capacity that may changealong the length of a weft thread as the latter passes through thesensor.

According to a further embodiment of the invention, the sensor outputsignals representing the parameters of the weft thread yarn as it ispulled off a supply spool, are supplied to an electronical controldevice including a computer, wherein the specific yarn parametersrelating to the air effectiveness, are calculated from said sensorsignals to provide impulse duration control signals to the relay nozzlescontrolled in groups, which are adjusted depending on such controlsignals.

Light yarns require only a short air impulse for their transport,especially at the outlet of the weft insertion air channel in thestretching phase, whereby the impulse duration for light yarns differsonly immaterially from the impulse duration at the input of the weftinsertion air channel.

For heavy yarns an air impulse of a determined length is produced at theinlet of the weft insertion air channel and the air impulse at theoutput of the weft insertion air channel in the stretching phase, islengthened substantially compared to the air impulse length at theinlet.

For light yarns it is, for example, necessary in the stretching phase tocarry the thread only by two relay nozzle groups, whereas for heavyyarns it is necessary to have the thread carried by three relay nozzlegroups which are controlled simultaneously.

These required different controls are automatically recognized by thecomputer depending on the yarn qualities manually inputted orautomatically supplied as currently measured by the sensors, accordingto the invention, whereby the relay nozzles are respectively controlledfor different durations.

In a further embodiment of the present invention the main nozzles arecontrolled in addition to the relay nozzles, in such a manner that byway of sensors in connection with an electronic control device, thestarting point of the yarns is determined when the yarn is introducedinto the weft insertion air channel. Thus, the advantage exists that inspite of different thread speeds which a light yarn has in the insertionair channel as compared to a heavy yarn, the threads arrivesimultaneously at the exit side of the air weaving machine.

Another advantage is seen in that the length of the stretching phase,that is the time for the stretching of the yarn is the same for bothtypes of yarns. Thus, a substantial saving of air is achieved for thegroups of relay nozzles allocated to the stretching phase, because theserequire only a relatively short duration control.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail in the following withreference to an example embodiment shown in the accompanying drawings,wherein:

FIG. 1 is a schematic plan view of the weft thread insertion componentsof an air jet loom equipped with sensors for measuring the current aireffectiveness of the several weft threads; and

FIGS. 2 and 3 illustrate details of the impulse duration control,whereby the ordinate in both FIGS. 2 and 3 shows time (t) inmilliseconds and the abscissa shows the distribution of the relay nozzlegroups along the weaving width of the loom.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT AND OF THE BEST MODE OFTHE INVENTION

The air weaving machine 1 according to FIG. 1 comprises a weaving reed 2in which an insertion air channel 3 is formed.

A plurality of relay nozzles R1 to R25 are arranged in a row extendingin parallel to the insertion air channel in the weaving reed 2, wherebythe relay nozzles R1 to R25 form nozzle groups I, II, . . . and soforth. In FIGS. 2 and 3 seven nozzle group numbers I, II, III, IV, V,VI, and VII are shown.

Each nozzle group I, II, . . . is controlled by a respectiveelectromagnetic valve 15 connected through a pressurized air conduit 16to the nozzles of its group and with a conduit 17 to a pressurized airsupply not shown. The valve 15 is constructed as an electromagnetictwo-way-valve.

The valve 15 is controlled through an electrical conductor 20 connectedto a control device 18 having an input terminal 19 such as a keyboardmerely indicated schematically by an arrow.

The yarn insertion side of the air weaving machine 1 is formed by aplurality of yarn reels 7, 8, whereby a weft thread 9, 10 is pulled offeach yarn reel 7, 8. Each weft thread is supplied to its respectivepreliminary reeling device 11, 12 through sensors 23 which currentlymeasure the air effectiveness of the respective weft threads 9, 10.

From the preliminary reeling device 11, 12, the yarn is guided to arespective main nozzle 13, 14 by an impulse controlled rod. The mainnozzles 13, 14 insert the respective weft thread 9, 10 into theinsertion air channel 3. The main nozzles 13, 14 are also controlled intheir air supply by electromagnetic valves 22 which are under thecontrol of the control device 18.

In accordance with the control of the magnetic valves 15 and 22 the airfrom a source of pressurized air, is supplied through the conduit 17 tothe respective output conduit 16' leading to the main nozzles 13, 14,and conduit 16 leading to the relay nozzles R1, R2, . . . .

According to the invention, each weft thread 9, 10 passes through itssensor 23, for example a capacitive sensor, which provides at its outputan electrical signal representing the current air effectiveness of therespective weft thread 9, 10 along its length as the thread movesthrough the sensor 23. The thread thickness and thus its hairiness maybe measured capacitively, for example, whereby the signals producedelectronically by the sensors 23 are supplied to the control device 18through signal conductors 25, 25'. The control device 18 processes thesesignals representing the currently measured air effectiveness of theweft threads 9, 10 to provide respective control signals on theconductors 20 for controlling the magnetic valves 15 and 22 leading tothe relay nozzles R1 . . . and to the main nozzles 13, 14 respectively,in accordance with the control signal. The sensors 23 may be combinedwith conventional thread guides 24.

FIGS. 2 and 3 disclose further details of the control. In both FIGS. 2and 3 the weaving width and the relay nozzle group numbers I to VII areplotted along the abscissa. The individual nozzle numbers R1 to R25 areindicated below the abscissa. The time is plotted in milliseconds alongthe ordinate. A slanted line 26 in FIG. 2 indicates the beginning of theair blowing operation of the relay nozzle groups I, II, . . . fortransporting a light weft thread 9 through the air insertion channel 3.A further slanted line 27 in FIG. 2 indicates the end of the air blowingoperation. Similarly, in FIG. 3 a line 26' marks the beginning of theair blowing while line 27' marks the end of the air blowing, except thatin FIG. 3 a heavy weft thread 10 is transported.

Referring to FIG. 2, the air supply to the relay nozzles R1 to R5 ofgroup I begins at ten milliseconds and ends at about twenty-fivemilliseconds. Therefore, the air supply to group I is controlled with animpulse length of about fifteen milliseconds. The air supply to relaynozzles R6 to R9 of group II begins at about fifteen milliseconds andends at about thirty milliseconds. Hence, the duration of the air supplyto the second group II is also about fifteen milliseconds. The sameapplies approximately to groups III and IV. The increase in the verticalspacing between lines 26 and 27 from left to right indicates that theduration of the air supply to the nozzle groups increases from theinsertion end to the exit end of the air weft thread insertion channel.For example, the air supply to the last two groups VI and VII continuesfor about twenty seconds each. The insertion of the light weft thread 9is completed at about sixty milliseconds.

FIG. 3 shows, as compared to the diagram of FIG. 2, a modified picture,whereby it will be recognized that the straight lines 26', 27' aresteeper than the respective lines 26, 27 in FIG. 2. This steepness showsthat it takes longer to insert a heavier weft thread 10 than a lighterweft thread 9. As a result, heavier weft threads have an increased airrequirement. It is further recognizable that in the range of thestretching phase, that is along groups V to VII, the duration of the airsupply pulses is lengthened at 28, 29, 30 for thus carrying andstretching the heavy weft thread 10. The insertion of the heavy weftthread is completed at about sixty-eight milliseconds and the last airpulse duration for group VII in FIG. 3 is about twenty-sevenmilliseconds. Especially, line 27' has been drawn as an approximationstraight line rather than a curve passing through the intersectionsbetween the vertical dashed lines separating the groups and thehorizontal lines indicating the end of the air supply to the respectivenozzle group.

The invention teaches modifying in a control device 18 yarn specificvalues manually entered through keyboard 19 into a memory of the controldevice 18, by currently measured air effectiveness representing valuesof the respective yarns forming the weft threads. The so modified valuesare used to provide respective control signals for controlling thedurations of the air supply to the respective relay nozzle groups.

The invention provides the essential advantage that heavy and lightyarns can be woven automatically in the same weaving operation at a highquality and at a low air consumption.

According to a modification of the invention the parameter of the aireffectiveness is calculated by a recognition of the yarn behavior in theair insertion channel. More specifically in this embodiment the yarnspeed in the air insertion channel is measured with the aid of a lightbarrier and based on this speed, the duration of the impulses iscontrolled through the control device 18.

Although the invention has been described with reference to specificexample embodiments it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims.

We claim:
 1. An apparatus for controlling an air supply to nozzle meansfor inserting weft threads of different yarn types into a respectiveshed in the air jet loom, comprising a control device for producing avalve control signal, said control device having stored therein specificyarn parameters representing said different yarn types, said controlsignal being produced in accordance with said specific yarn parameters,electrically controllable valve means for supplying pressurized air tosaid nozzle means, control conductor means connecting said valve meansto said control device for controlling a duration during which saidvalve means are switched open to produce air jets of respectivedurations in response to said control signal, sensor means arranged tosense values representing a present air effectiveness for each yarnprior to said inserting, further conductor means connecting said sensormeans to said control device to form a closed loop control circuit forsupplying said present air effectiveness values to said control devicewhich modifies said control signal in accordance with said present aireffectiveness values, whereby said control signal is formed in responseto said stored specific yarn parameters and modified in response to saidpresent air effectiveness values.
 2. The apparatus of claim 1, whereinsaid sensor means comprise means for measuring a thickness of saidyarns, said thickness representing said present air effectiveness. 3.The apparatus of claim 2, wherein said sensor means comprise acapacitive sensor for measuring the thickness of each weft thread. 4.The apparatus of claim 1 wherein said nozzle means comprise relay nozzlemeans and main insertion nozzle means, said relay nozzle means beingarranged in groups along a weft thread air insertion channel, said valvemeans comprising a separate valve for each relay nozzle group and atleast one separate valve for said main insertion nozzle means.
 5. Theapparatus of claim 1, wherein said sensor means are arranged upstream ofan air insertion channel as viewed in a movement direction of said weftthread, whereby said sensor means provide information to said controldevice as to when a weft thread enters into said air insertion channel.